(a) Field of the Invention
The present invention relates to an apparatus and method for performing fast transform at the receiver of a communication system.
(b) Description of the Related Art
In general, the receiver of CDMA (Code Division Multiple Access) communication systems employs the FHT (Fast Hadamard Transform) method so as to demodulate the modulated signals from a mobile station. Namely, a IS95 CDMA base station, upon receiving backward transmit signals, performs the FHT method to demodulate the FHT-modulated signals from the mobile station by using one of 64 Hadamard orthogonal codes according to the 6-bit information of the mobile station user used as an indicator. In this way, the receiver of the CDMA communication systems can receive the signals efficiently.
The receiver of OFDM (Orthogonal Frequency Division Multiplexing) communication systems demodulates FFT-modulated signals from the mobile station by the FFT method. In this way, the receiver of the OFDM communication systems can receive the signals efficiently.
However, the FHT receiver has a different structure from the FFT receiver, so each of the receivers is to be implemented in separate hardware specifically by the communication systems.